At the time of starting up a vehicle (including the time of restarting up the halted vehicle) or at the time of braking the vehicle, a conventional diesel hybrid vehicle system executes control to stop a diesel engine to cause the vehicle to run on electric power supplied from a storage battery in order to reduce exhaust emissions. In a case where a diesel hybrid system is used for a railway vehicle, the diesel hybrid system executes control to stop a diesel engine or to reduce an output of the diesel engine even when the vehicle coasts.
When the diesel engine is stopped or the output of the diesel engine is reduced, the vehicle generates less noise, and accordingly the volume of sound for circumstances around the vehicle to recognize the presence of the vehicle (a vehicle recognition sound) is reduced. In order to compensate for reduction in the volume of the vehicle recognition sound, there has been proposed a conventional diesel hybrid vehicle system in which a simulated sound generator that generates a simulated vehicle running sound is incorporated in a vehicle (for example, Patent Literature 1).